1. Field of the Invention
This invention generally relates to a distributor for internal combustion engine and a distributor rotor electrode employed therein, and more particularly, to a distributor and a distributor rotor electrode designed to suppress noise radio waves resulting from a spark discharge consequent to the distribution of power.
2. Discription of Related Art
FIG. 1 shows a side elevational view, partially in section, of a conventional distributor for internal combustion engine. A rotrary shaft 1 of the distributor rotates in synchronization with rotation of a crank shaft of the internal combustion engine. A distributor rotor 2 fixed to the rotary shaft 1 is provided with a distributor rotor electrode 3. Also provided are a plurality of lateral electrodes 4 spaced a discharge gap (g) from a rotation orbit of the distributor rotor electrode 3. A contact 6 connected with an ignition coil through a leading wire 5 is pressed in contact with an upper surface of the distributor rotor electrode 3.
In the above structure, every time the distributor rotor electrode 3 comes close to the lateral electrodes 4 in accordance with the rotation of the distributor rotor 2, a high voltage is applied to the lateral electrodes 4 as a result of discharge via the discharge gap (g). This discharge via the discharge gap (g) allows a sequential distribution of power to an ignition plug of each cylinder. At this occasion, the spark discharge in the discharge gap (g) between the distributor rotor electrode 3 and lateral electrodes 4 generates noise radio waves causing radio jamming or interference to radio and television broadcasting, various kinds of radiocummunication system and electronic system, thereby deteriorating S/N ratio.
In order to suppress the generation of noise radio waves discribed above, conventionally, means disclosed in Japanese Patent Publication No. 51-38853 has been employed, which has, as indicated in FIG. 2, a highly resistive layer 7 formed on the surface of the distributor rotor electrode 3 adjacent to the lateral electrodes 4. Such structure as is possessed by the above-discribed means can reduce the strength of electric field of noise radio waves generated at the time of discharge between the distributor rotor electrode 3 and lateral electrodes 4.
Although it is confirmed by the peak detection (SAE) that the conventional distributor for internal combustion engine in the foregoing structure is considerably effective to suppress noise radio waves owing to the highly resistive layer provided in the distributor rotor electrode, the quasi-peak detection (CISPR) of the conventional distributor does not show satisfactory effect. Therefore, the earlier-mentioned radio jamming due to the noise radio waves particularly in FM radio is yet to be solved in the conventional distributor.
Moreover, the highly resistive layer on the front face of the distributor rotor electrode increases radio noises, resulting in unstable discharge. In addition, the highly resistive layer has a drawback to be weak to discharge.